1. Field of the Invention
The present invention is broadly concerned with doubly modified waxy barley starch products exhibiting extraordinary freeze-thaw stability together with good thickening power, clarity and paste stability making the starch products particularly useful in the context of food systems (e.g., pie fillings) typically subject to freeze-thaw cycles. More particularly, it is concerned with such waxy barley starch products, together with resultant food systems containing the same, wherein waxy barley starch is both cross-linked and hydroxypropylated to achieve the outstanding freeze-thaw stability characteristics of the invention.
2. Description of the Prior Art
Barley (Hordeum vulgare L.) is the world's fourth most important cereal crop, after wheat, maize, and rice. Roughly, its production is two-fifths that of wheat. It is grown over a broader environmental range than any other cereal. Much of the world's barley is produced in regions with climates unfavorable for growing other major cereals. During the past two decades, the harvested area of barley in the world has increased faster than those of rice, although not as rapidly as those of wheat or maize.
Barley has two principal commercial uses. One is for livestock feed and the other is for malting. The use of barley for human food is mainly found in regions where other cereals do not grow well due to altitude, latitude, low rainfall, or soil salinity. In the U.S.A., approximately 2% of the barley production is used for food products. In Western Europe, barley has also been used for industrial starch production.
In the early 1970's, waxy Compana barley was developed at Montana State University based on the generalization that waxy starch is superior to normal starch for many food uses. The source of the waxy gene in the Montana State barley-breeding program was waxy Oderbrucker. Compana was chosen as a parent cultivar because of its large kernel size and high yield; it is a two-rowed spring barley grown in Montana for many years as a feed barley. It has also been suggested that a waxy barley variety with good agronomic properties would provide a new source of raw material for the production of waxy starch. In recent years, it has been pointed out that the beta-glucans in waxy barley would be a valuable source of dietary fiber since they may reduce serum cholesterol.
Starches are added to processed foods primarily as functional ingredients. They provide the characteristic viscosity, texture, and stability to many food products. The highly viscous paste of waxy maize starch has led to its extensive use as an unmodified starch and a base for making a broad line of modified starches for thickening and texturizing foods, as well as for industrial application.
It is known that cooked pastes of normal-amylose starches at 6-15% starch solids set to a stiff gel when cooled; while under the same conditions, non- or low-amylose waxy starches form a viscous sol. It is believed that this characteristic difference accounts for the lack of utility of waxy starches in certain food systems.
For example, normal barley starch can be substituted for wheat starch in bread making. However, when wheat starch in bread was replaced with low amylose waxy barley starch, the microloaf collapsed upon cooling, or the pup-loaf shrank excessively. The collapse or shrinkage of the cooled bread indicates that the viscous sol of the cooked waxy barley starch was too deformable to support the loaf and that denatured gluten does not perform that function alone.